1. Field of the Invention
This invention relates to a cold padding batch dyeing process for tubular knitted fabrics.
2. Description of the Prior Art
Dyeing of tubular knitted fabrics is usually conducted by a dip dyeing process in which a wince or jet dyeing machine is used. As this process is a batch process, however, its production efficiency is low, and it requires large quantities of auxiliary raw materials, water and fuel.
A cold padding batch dyeing process has, therefore, been developed and is known as an effective method in certain fields of application. In order to employ this process for dyeing a tubular knitted fabrics, however, it is necessary to cut and open the fabric into a shape similar to a woven cloth. Difficulty is involved in winding the fabric. The fabric is also difficult to handle as it must be kept in the open shape when passing through all the steps of soaping, softening and drying following the dyeing step. Thus, extensive and costly equipment is required for the dyeing of tubular knitted fabrics by the conventional cold padding batch process.
The cold padding batch dyeing process is known for a lot of advantages, including fine color reproducibility, highly efficient use of a dye, saving of dyeing auxiliaries, energy saving, low water consumption, and low equipment costs. Special care must, however, be taken for the preparation of the fabric to be dyed in order to accomplish uniform padding. The cold padding batch dyeing process is conducted at a padding temperature of about 20.degree. C., and further involves a temperature as low as 10.degree. C. to 30.degree. C. for the ageing purpose. It does not include any dyeing step requiring a heat treatment, therefore, the success of dyeing depends on the uniformity of padding. The mere application of the process unavoidably results in the development of edge marks and unevenness of dyeing on the opposite sides of the fabric. In order to eliminate these inconveniences, it is necessary to ensure uniform penetration of a dye solution into the fabric to be dyed and maintenance of a homogeneous fabric structure.
If it is desired to keep a tubular knitted fabric in tubular shape for padding with a dyeing solution, the fabric is necessarily flattened into a two-ply shape, and the edge portions of the fabric are dyed to a higher density than the rest. After padding, the fabric cannot be squeezed satisfactorily by mangles of hard rubber used in the conventional cold padding batch process. Even if the squeezing pressure is regulated, thinner or thicker streaks are very likely to remain along the edges of the fabric.
It has, therefore, been proposed to use mangles formed from a softer rubber, and mangles of rubber having a Shore hardness of, 60, for example, have been found satisfactory for eliminating edge marks to thereby obtain a substantially uniformly dyed fabric. The mere use of such improved mangles is, however, not sufficient for complete removal of edge marks.